The problem of disposing of municipal waste in the United States has grown to epic proportions of imperative immediacy. EPA statistics indicate that 440 tons of solid waste are produced each day. After sorting out the resource recoverable metals and glass, 378 tons or 86% of the total mass is generally buried in what are erroneously referred to as sanitary landfills. However years of unrestrained use of vacant land for this purpose has virtually exhausted the availability of garbage dump sites within economically close proximity to the centers of greatest waste generation, large metropolitan cities. The potential of landfills for contaminating the atmosphere and water supply of such demographic concentrations has now become all too evident.
While recycling and resource recovery are appealing they also have limitations. Newsprint and corrugated material can only be recycled a limited number of times inasmuch as the length of the fiber decreases each time that it is hydro-pulped back into paper stock. When tensile strength decreases, binders are increased, making it less suitable for recycling due to the higher cost of removing the additive binders. Each element except metals and glass has a finite life beyond which it ceases to be suitable for reuse or recycling. Thus recycling does not eliminate waste but only postpones its ultimate disposal. Aluminum remains the chief source of revenue, subsidizing the labor intensive hand sorting required in recycling operations. While recycling constitutes a useful adjunct to waste reduction at its source, recycling does not reduce the remaining 86% of the waste that has limited intrinsic value.
While uncontrolled open incineration would send contaminating noxious gases and particulate matter into the atmosphere the technology now exists to control stack emissions to protect the atmosphere from toxic pollutants. Thus plants for deriving energy from incineration of waste such as in Commerce, Calif., successfully operate with very low impact on air quality. It is believed that plants of this type could become models for future facilities as part of an ultimate solution to the current waste crisis. Fluidized bed technology increases the available oxygen to the fuel in these new generation incinerators, elevating the combustion temperature for more complete burning with minimal stack emissions. Scrubbers and precipitators trap monitored pollutants before they escape.
The high incidence of plastics that pervade today's waste stream possess potentially high heat generation values, almost twice that of bituminous coal used for power generation. Polyethylene, the most popular packaging wrap and food container plastic, will generate 19,950 BTU's per pound under controlled conditions in properly designed incinerators. In comparison bituminous soft coal, which varies according to the acid rain producing sulfur content, generates from 10,000 BTU/lb. to 12,500 BTU/lb. The less costly higher sulfur content coal produces more usable heat but also more acid rain producing sulfur dioxide. A random sample of processed municipal garbage containing a mix of various plastics in addition to the usual organic matter will average 13,850 BTU/lb. using fluidized bed combustion principles.
Most such incinerating (WTE) facilities operating today are at or near capacity due largely to the unpredictable composition of unclassified waste which they receive. Moisture laden organic garbage must be interspersed with dry combustibles to assist in maintaining the minimum 1800.degree. F. necessary for complete combustion. Conceivably a continuous flow of dehydrated, uniform size particles in a heterogeneous mix, could appreciably increase the through-put capacity of such WTE systems, lowering operating costs while maintaining optimum combustion efficiency. Should processing for bulk and moisture reduction be performed at the generation point where recyclables are sorted, hauling costs would decrease. Maximum density loads without the liquid weight could boost truck payload capacity.
Processing to fragmentize and dehydrate solid waste to this desirable state could create an inexhaustible supply of readily usable fuel for energy. Should the processing be accomplished on-site at the point of generation, additional economies could be realized through fewer pick-ups of higher density loads. This form of fuel derived from waste could conceivably create a sought-after commodity rather than be subjected to "tipping" fees since it would not require additional handling or inspection, rendering it the ideal substitute for coal in existing fluidized bed boilers. In addition to these apparent economic incentives, on-site processing as an adjunct to properly designed and operated incinerating (WTE) facilities offer a logical and advantageous approach toward easing the waste management crisis while lessening dependence upon foreign imported oil or domestic fossil sources.